BUENAVENTURA, Colombia — One day in the middle of August, a gaunt 20-year-old who goes by the name of Jeilinapproached a middle-aged man and shot him several times in the chest with a pistol, killing him. The victim was a carnicero, a butcher, who worked in the San Pedro neighborhood of Buenaventura, a sprawling, rain-soaked port city on Colombia’s Pacific coast. The butcher’s offense was simple enough, Jeilin explained: He refused to pay the two months’ worth of extortion money, about 400,000 pesos (or roughly $200), to the gangs who control the city’s streets. What’s more, Jeilin said, the butcher had threatened to call the police.

“I shot him with a 9 millimeter,” he said, “four times, to be sure he was dead.”

Jeilin and I met in a hotel room not far from his home turf, a quadrant of streets in a waterfront neighborhood called Santa Monica, where rickety wooden shacks on stilts jut out precariously over the brackish water of the bay. Wearing a black wool beanie, a T-shirt, blue jeans, and a pair of green Nike sandals, Jeilin was unassuming, but he explained that he was a primero—a kind of block leader for his gang, known as the Gaitanistas. Along with the Urabeños and La Empresa, Jeilin’s gang is one of three main armed groups that control large parts of Buenaventura’s waterfront through a combination of extortion, murder, kidnappings, and threats. For now, the Gaitanistas are the weakest of the gangs, but Jeilin said that his bosses have ordered him to keep fighting until the group controls the city completely. “That’s the mission we have,” he explained, “to keep our territory and to expand it.” Was he ever afraid? He shook his head: “I’m not scared. When it’s time to die, it’s time to die.”

Left, roughly 60 percent of Colombia’s imports and exports pass through the port of Buenaventura; right, a street divides Buenaventura’s historic neighborhood of San José and an area of hotels and commercial buildings.

Buenaventura is often described as Colombia’s most violent city. Its homicide rate is 56 percent higher than the national average, and nine times that of New York City. An expansive port system has turned the city into the gateway for roughly 60 percent of Colombia’s imports and exports, but very little of the profits have trickled down to residents. In 2013, some 15 million tons of legal goods, along with untold quantities of illicit drugs and weapons, passed through Buenaventura. The mix of high-end development prospects, a strategic international port with easy access to Asia, Europe, and North America, and the city’s poverty—roughly 80 percent of the population is considered poor—has helped make Buenaventura a battleground for all sorts of competing interests, legitimate and criminal alike. Often called bacrim, for bandas criminales (criminal bands), Jeilin’s group and others like it fight each other over drug-trafficking routes, but also for control of valuable waterfront property, which large companies are, in turn, eyeing for high-end development.

For decades, the Colombian government paid scant attention to the stretch of Pacific coastline where Buenaventura sits. With the exception of the port, the state largely abandoned these areas, leaving Buenaventura and its residents—mostly Afro-Colombian descendants of slaves—isolated and impoverished. Geographically separated from the rest of Colombia by the Andes Mountains, the city is a signature of government indifference and continues to lack the necessary infrastructure that could connect Buenaventura with the rest of the country.

In 2012, Colombia joined the Pacific Alliance, a trading bloc that includes Mexico, Peru, and Chile, whose principle aim is to aggressively pursue economic ties with Asia, in particular China. But when government officials presented Buenaventura as a location for a Pacific Alliance summit the following year—a Pacific gateway to South America, the city had the region’s largest port and could establish Colombia as a key player in the Pacific Alliance, the thinking went—the idea was shot down because the city was far too dangerous. The summit was ultimately held hundreds of miles away on the Caribbean, serving as a wake-up call for those intent on moving the country into the next century. Since then, President Juan Manuel Santos has worked with city officials to improve Buenaventura’s image by developing an aggressive plan to promote tourism and downtown development that includes a multimillion-dollar waterfront esplanade and luxury hotels. But the state of affairs in this city have made such an about-face nearly impossible.

Colombia faces serious obstacles as it struggles to put 50 years of conflict behind it, and economic renewal is just part of Santos’s plan to emerge intact from the guerrilla war that has pitted successive administrations against the Revolutionary Armed Forces of Colombia (known by its Spanish acronym of FARC). Peace talks, which began in October 2012 and now continue in Havana, Cuba, could potentially put an end to Latin America’s longest-running conflict. But the problem is that, while the government is making progress on negotiations with the FARC, there are consequences of the war—seen most extremely in Buenaventura—that aren’t likely to be healed by the peace process. Years of fighting, combined with a largely absentee government, have turned Buenaventura into a kind of feral place in which Jeilin and the other members of the bacrim—descendants of paramilitary groups that once fought the FARC—operate with impunity.

Unless Santos’s government can deliver, quickly, on promises to tend to the consequences wrought by years of neglect, Buenaventura is only likely to become more violent, with or without a national peace agreement. And that could be disastrous for Colombia’s long-term vision for its future.

A man sits in Buenaventura’s Pueblo Nuevo neighborhood.

More than 220,000 people have died in Colombia’s war, thousands more have been wounded, and some 6 million have been internally displaced. All told, around 6.7 million people are considered victims of the conflict. The government and the FARC first tried in 1984 to engage in peace talks and have continued to try, in vain, ever since. That year, the Colombian government promised widespread changes, including agrarian reform, increased political participation, and a reconciliation process. But when these reforms failed to materialize and the commission that the government had established turned out to be ineffectual, the talks quickly broke down, and the FARC ramped up its campaign of attacks and ambushes.

For those in Buenaventura, the neighborhood is the new battlefield.

Within a few years, the conflict became even more volatile. Landowners and small-business owners, outraged by the continued campaign of kidnappings and extortion, began backing right-wing paramilitary groups in Buenaventura, often with the tacit knowledge of the Colombian National Army and government. The most prominent of these paramilitary groups, the United Self-Defense Forces of Colombia (AUC), employed many of the same tactics of the FARC—assassinations, kidnappings, and massacres, often of civilians—in their bid to beat back the rebels. By this point, however, the FARC was actively engaged in large-scale drug trafficking to help fund its operations, increasing the nebulous ties among organized crime, terror, and economic survival.

In 2003, Colombia, under then-President Álvaro Uribe, undertook a massive campaign to “demobilize” some 32,000 paramilitary fighters who had joined the war, often at the behest of small-business owners who were more vulnerable to extortion campaigns by the FARC. As part of the campaign, the government also signed a peace deal with the AUC and offered fighters reduced prison sentences in exchange for laying down their arms. But the government didn’t provide job training or education programs to many of these ex-paramilitary fighters. Consequently, they began drifting back into drug smuggling and criminality, and, as such, the bacrim was born—a network that overwhelmingly consisted of people who had been caught up in the war, on both sides. On the streets, the bacrim members applied the same zeal to their lawless endeavors as they had as soldiers. Some former FARC members trafficked drugs, for instance, using the very networks that had helped them fund the war. And Buenaventura, with its open ocean access and general lack of rule of law, proved more than fertile ground for the bacrim to prosper.

Left, a woman holds her child in Buenaventura’s San José neighborhood; right, a man sits in Buenaventura’s La Playita neighborhood.

If there was any hope for ex-combatants to trust the government’s promises, that was squashed in 2006, when the government—which had promised former fighters protection from extradition during the demobilization process— began sending some of them north to the United States to face drug-trafficking charges. Supporters of the paramilitaries thought the government had betrayed its promise to protect them, while relatives of those whom the paramilitaries had killed lost hope they would ever learn what happened to their loved ones.

Today, President Santos is so committed to the peace process that he pegged his narrow re-election campaign to it, and recently he has had to push hard for patience and tolerance with a public that has grown wary of both the rebels and government rhetoric. The meetings in Havana have been plagued by setbacks, threats by both sides to walk away, and continued attacks and counterattacks as the FARC and government leaders jockey for position and leverage. (Other rebel groups are not part of the talks, and the government recently announced separate negotiations with the National Liberation Army, or ELN.)

But there also have been scenes of hope. In late August, Gen. Javier Flórez, the Colombian military’s second-highest officer, met with senior FARC officials in person—the first time a serving general in Colombia has agreed to such an intimate and public encounter with sworn enemies. One of the FARC’s top negotiators, Iván Márquez, said the meetings were a chance to talk “warrior to warrior.” The meeting signaled that the two sides had opened discussions about the decommissioning of weapons and had moved one step closer to a final agreement.

But for all the optimism the peace talks have generated in Cuba—and, to a lesser extent, Colombia—for the residents of Buenaventura, the talks might as well be happening on another planet. When Santos visited the city this past April, he vowed to develop job-training programs for young people, as well as increased credit lines for small businesses. The FARC responded by exploding a makeshift bomb at Buenaventura’s central electrical tower, leaving the city dark for days. “Control of Buenaventura means control of the national economy of Colombia,” said Víctor Vidal, a local council member and outspoken critic of government inaction in Buenaventura. “And as long as the ships keep coming and going and the port is working, no one cares about the deaths in these neighborhoods. No one cares.”

That is to say, for those in Buenaventura, the neighborhood is the new battlefield.

In March, Human Rights Watch published a damning report documenting widespread human rights abuses in the city, including scores of murders, dismemberments, and disappearances. One of the more disturbing revelations was the existence of several casas de pique, or chop houses, where gangs torture their victims by cutting them to pieces—sometimes while the victims are still alive. They then throw the body parts into the ocean.

This spring, residents of Puente Nayero, a small sub-neighborhood that juts out into the bay, found themselves sandwiched between two warring bacrim groups, the Urabeños and La Empresa. At the end of one long street was a chop house. “They were killing people in front of kids; they were taking houses,” said resident William Mina. “The community was scared.” The 19-year-old remembers gangsters pulling people down the street and into the wooden shed. He remembers the screams.

Faced with daily death threats and terrorized by the violence, a group of leaders had little choice but to organize themselves into a neighborhood watch and self-defense coalition to confront the tyranny of the gangs. With the help of the police and the Inter-Ecclesiastical Commission of Justice and Peace, part of the World Council of Churches, an NGO that places volunteers in violent communities as “witnesses,” they walled off overnight the entrance to their street with wooden barriers and declared Puente Nayero a violence-free “humanitarian zone”; one of their first acts was to tear down the chop house. Today, some 290 families live inside, yet the gangs—desperate to expand their territory—continue to threaten the residents.

A humanitarian zone existing on a single street anywhere seems improbable—and it is. But for all its fragility, the zone does provide a necessary sanctuary for a beleaguered population. Near the entrance to the humanitarian zone, residents turned the wall of a house into a public mural with a hand-painted charter: #1 We will never use any kind of violence; #5 We will protect each other inside the humanitarian space; #6 We will take turns guarding the doors.

Nevertheless, when local children argue with each other, they resort to a language they know works. Te voy a picar, they say: I’m going to cut you up. “It’s easy to get the paramilitaries out,” said 22-year-old Fleiner Angulo. “But it’s hard to get the violence out of your head.”

In April 2014, a fire destroyed some 30 homes in Buenaventura’s Santa Fe neighborhood.

Few neighborhoods in Buenaventura haven’t been affected by violence, and some have been emptied completely as residents succumb to pressure and flee. According to Human Rights Watch, some 56,000 people were displaced in and around the city from 2010 through 2013, more than in any other municipality in Colombia. Many of these were children who became prey for gangs that are constantly on the lookout for new recruits. Although there are no official tallies of how many kids have been conscripted, Father Adriel Ruiz, who runs a parish and community center in a particularly rough neighborhood called barrio Lleras, estimates that as many as 4,000 children have been swept into the bacrim in recent years.

Julio César Biojó has seen a generation of children disappear into this underworld in the Palo Seco neighborhood, a jumble of half-finished wooden huts, open sewage canals, and rocky, trash-strewn dirt lanes.

A native of Buenaventura, Biojó says the bacrim first appeared in his neighborhood in 2005 and immediately held a community meeting in a nearby school. They were there to protect the neighborhood, they told the residents. Over time, however, the newcomers began recruiting children and teaching them how to fight—and the children have since become the lifeblood of the bacrim.

In 2008, a group of armed men from La Empresa forced Biojó out of his home at gunpoint; they wanted to control the neighborhood, and he had refused to budge from his lot. He only returned in 2012, when control of the neighborhood had passed to the Urabeños and his former tormentors had been driven out. The new gang, he explained, wasn’t necessarily a safer option, but, for the time being, the men who had threatened his family were gone. “We can’t go against any of them or else we face assassination,” he said. “So if you want to save your children, you have to find some other way to do it.”

That year, he set out to help the community. With some meager government assistance, he created a safe haven where kids can read and play music. The NGO, called the Junta de Acción Comunal (Community Action Group), is run out of a cement building with bars on the windows. His own children, two boys and a girl, are frequent visitors. It’s a far cry from a high-end day care or anything even resembling one, but it provides kids with a sense that there is at least one place outside their homes where they can feel a modicum of safety and where the bacrim might leave them alone.

Left, vendors sell seafood at a market in the Pueblo Nuevo neighborhood; right, residents walk through a market in the Pueblo Nuevo neighborhood.

Jeilin, the primero and assassin for the Gaitanistas, was one of the unlucky ones—a child who fell into the gangs early on. He was 13 years old in 2007, when two men from the Urabeños broke into his home while his family was eating a dinner of chicken and rice and shot both of his parents in the face as he watched. That year, Jeilin’s cousin Longi, himself a gang member, taught Jeilin how to use a machete, then a gun, and finally schooled Jeilin on “technical things,” such as how to dismember people properly.

Around that time, Jeilin said, he first participated in a murder. The victim was a woman who had transgressed somehow—it was never clear to Jeilin exactly what her crime was. Led by an older man, Jeilin and the other kids helped hack her to death with machetes. “Then we cut her up and put her in the ocean, and I went home,” Jeilin said. “I went back to normal.”

Jeilin’s gaze is vacant and cold, and he expresses no remorse for his victims, though he did concede that thinking too much about his parents is difficult. “I feel sad for my family, but they already killed them. There’s nothing to think,” he said, explaining that what he does now is for them, “and it’s also part of my job.” In total, Jeilin said, he has killed eight people. Many of them he dismembered “finger by finger” afterward. Some of them he burned. Most wound up in the ocean. “If I get an order to kill,” he said, “that’s it.”

A man stands in Buenaventura’s historic San José neighborhood.

In many respects, Buenaventura has already crossed a Rubicon of sorts, from being a city where police can be effective to one where a quasi-military occupation is required just to prevent complete anarchy. The violent waterfront neighborhoods in particular are swarming with police officers, all of whom are equipped with automatic assault rifles, pistols, and fatigues that make them look much more like soldiers than police. Virtually every corner of these neighborhoods is manned by at least one officer, often two.

Colombian officialdom insists that violence has been decreasing in Buenaventura. In late October, President Santos visited Buenaventura again and claimed that a security plan called Vamos Seguros (Let’s Go Safely) had led to a 25 percent reduction in crime in Colombia’s 11 biggest cities, including Buenaventura, within the first week of implementation. According to the president’s website, seven drug-trafficking rings and more than a dozen armed-robbery outfits had been shut down.

When I visited in September, Col. José Miguel Correa, the commander of the local police force, similarly claimed that progress was already underway in Buenaventura. Sitting back in his chair, he pulled out a data sheet and began ticking off numbers—262 arrests of Urabeños and La Empresa members in 2014, including 26 leaders of both groups; 177 firearms confiscated; 2,732 kilos of drugs impounded—and said the progress was partly a result of increased pressure from Santos’s Let’s Go Safely plan and Buenaventura’s strategic importance in Colombia’s national narrative. “The geographic location, the peace process, our economic growth—all of these things are very important here,” he said. “It was terrible here, but the police have started to attack back, and that has weakened the gangs.”

In early September, Colombian National Police and U.S. Drug Enforcement Administration operatives nabbed two leaders of La Empresa during a raid in Panama. Édgar and Ever Bustamante were believed to be responsible for large-scale drug- and money-smuggling operations in Buenaventura. “The police here are making spectacular progress,” Correa said. “Criminal activity is going down, and it’s limited to the gangs.”

But many people in Buenaventura question this claim, maintaining that the police are complicit with the gangsters, actively working with them to keep revenues from the drug trade flowing. Even the district attorneys responsible for bringing criminals to justice express skepticism about the loyalty and diligence of the police with whom they work.

When I was searching for evidence of Jeilin’s murderous exploits, a highly placed official at the district attorney’s office agreed to speak with me on the condition that I not use his name. Rifling through a stack of blue and tan folders piled on his desk, he pulled file number 02417, which belonged to a butcher who was killed in the San Pedro neighborhood, a warren of alleys, shacks, and canneries where fishermen sell their daily catches. That sounded like the crime Jeilin had described.

The official looked at the file and frowned. “It doesn’t say why he was picked up, and that worries me,” he said. There was a killing and an arrest, but the paperwork shed no light on whether they were connected. The stories he came across in his docket every day said as much about the authorities’ incompetence and corruption as they did about the criminal networks operating in the city, he believes. Even with a functioning, ethical police force and a fully staffed prosecutor’s office, he said, the violence in Buenaventura would still be overwhelming.

The official told me that he had reviewed 19 murder cases between July and September, and he pointed behind him to three large cardboard boxes filled with more pending cases—about 90 in total. Many of the victims were innocent merchants caught up in the violent politics of extortion, he said. But this caseload doesn’t even take into account a portion of the other types of crimes, he said, such as kidnappings and disappearances, that are also routine occurrences.

“There’s a capture of a gangster every day here, but it doesn’t make a difference,” he said. “You get captured, and there’s always someone to replace you.” What the city really needs, he added, is massive investment in infrastructure, education, and health. The peace process is a good thing, he said, but until these other, deeper problems are addressed, “the violence won’t stop—there’s too much misery.”

Residents of the San José neighborhood peer outside their home, a shack built on stilts.

The Colombian state has been absent for so long in Buenaventura, Father Ruiz told me, that “the people have started living in a kind of anarchy.” In that kind of environment, the prospect of thousands of trained soldiers, guerrilla fighters, and paramilitary thugs wandering around looking for work, or food, or simply a means to survive, is a sobering one.

One evening I met with a former paramilitary soldier who had gone through the demobilization program; he requested anonymity. Originally from a rural area called Pital, he was recruited in 2001 into the Bloque Calima, a notorious paramilitary organization. He was uneducated and illiterate, and the paramilitary group offered him 700,000 pesos a month (about $350). That same year, in April, he was involved in an infamous chainsaw massacre along the banks of a river, which flows down from the mountains toward Buenaventura. A few weeks later, the group’s leader forced him to kill a friend, apparently for a minor infraction involving a rifle. For some commanders, he realized, “the weapon was worth more than the man.”

Scared and emotionally overwhelmed, the soldier entered the demobilization program. And though he received modest payments from the government, he didn’t receive any job training or education. Eventually, the money ran out.

He can’t return to his ancestral village along the river because too many people who sympathize with the FARC are still there, and his affiliation with the paramilitary groups would be a death sentence. So he’s scraping by in Buenaventura as yet another possible recruit for the gangs who control the city.

Even with a functioning police force and a fully staffed prosecutor's office, the violence in Buenaventura would still be overwhelming.

“I never want to touch another weapon in my life,” he said. “But what I don’t know is if the weapons are going to touch me.” In other words, with no prospects and no further support from the government, he may find that his only means of survival involve crime.

“I went in ignorant, without thinking about my life and the future, and my ties to the community are broken,” the ex-paramilitary soldier said. “I just want the government to help me keep the promise we both signed.”

On Buenaventura’s waterfront sits the neighborhood of Colón, which, like the others, is little more than an assemblage of shanties. Several former FARC rebels occupy one set of houses at the end of a dirt road. Nearby are several known members of the Urabeños, who in recent years have taken control of the neighborhood. Here, in this forgotten corner of the city, the guerrilla war seems like a distant memory, but the threat of violence to everyone remains stark.

Although I understood the toll that violence is taking on Buenaventura’s residents, in the first week of my reporting I hadn’t seen any bloodshed myself. That all changed one late afternoon, when it was still bright outside and the streets of Colón were filled with people. I was getting into a car when a shot rang into the air. A crowd, screaming and crying, ran away from the noise and toward the water. In their midst, a large man held a woman by her hair and dragged her across the street; both of them were shouting. The man carried a pistol and pointed it at the woman’s head.

Moments later, at least four more shots rang out.

The street mostly emptied except for a small number of spectators. About 50 feet away from me, lying by the side of a black Kia sedan, was the woman, a 42-year-old wife and mother of two named Yolanda del Socorro Guerrero, the 16th woman murdered in Buenaventura this year. She ran a small business selling panela, or brown cane sugar, and according to witnesses and police, she had come to Colón to meet a customer. It emerged later that she had probably refused to pay the requisite bribe to the local gang, in this case the Urabeños, and for that she was murdered.

None of the residents told the police they saw anything; saying too much was dangerous. Meanwhile, Yolanda’s killer disappeared on the back of a motorcycle, trailed by a small car with black tinted windows. Around Yolanda’s head was a large pool of blood and, on her back, a large smoke burn, indicating that the last bullet was fired at short range, when she was already down, the latest assassination of 2014.

Scott C. Johnson is the former bureau chief for Newsweek in South Africa, Mexico, and Iraq. His book, The Wolf and the Watchman: A Father, a Son, and the CIA, was longlisted for a National Book Award in 2013.